Injection molding is performed by carrying out a mold clamping step of closing a mold to perform mold clamping, an injection step of injecting a material into the mold, a mold opening step of opening a mold after the injected material solidifies, an ejecting step of ejecting a molded product anchored to the mold, and the like. Additionally, an injection molding machine that carries out such injection molding includes a plurality of hydraulic actuators for carrying out respective steps, and a hydraulic supply device for supplying working oil to the hydraulic actuators. A pressure control or a flow rate control is executed by the hydraulic supply device to make the hydraulic actuators generate driving forces to carry out the respective steps.
As hydraulic supply devices of such injection molding machines, there are known hydraulic supply devices including a hydraulic pump that variably control the rotational speed of a servo motor connected to a servo circuit so as to control a discharge flow rate (for example, refer to Patent Document 1 and Patent Document 2). Additionally, the hydraulic supply device of the injection molding machine of Patent Document 2 includes a plurality of hydraulic pumps and a plurality of servo motors that rotationally drive the hydraulic pumps. Therefore, a large-sized drive motor can be made unnecessary, and regions where the capacity of the drive motor does not suit can be reduced, and stability of control can be achieved.